The invention relates to an extrusion head for producing flat profiles from rubber or plastics material mixtures.
A typical example of such a flat profile is a tread strip for automobile tires. In order to produce a tread strip for tires, it is necessary for three different types of mixtures to be combined because the strip comprises a tread surface made of a highly wear-resistant material, lateral portions made of highly compressible material and a so-called lower or base portion which forms the bottom layer of the tread surface and is usually formed from a softer mixture than the tread surface.
These three mixtures have markedly different viscosities but must be brought together in a single extrusion head to form the tread strip. Moreover, the mixtures must flow in flow channels in the extrusion head at substantially identical flow rates.